Dual-circuit, hydraulic brake systems are known in which the brake system comprises a first brake circuit, a second brake circuit, a dual-circuit brake actuator, such as a master brake cylinder, a first control line and a second control line. In such conventional systems, the first brake circuit has a first valve for regulating the brake pressure in the first brake circuit, the second brake circuit has a second valve for regulating the brake pressure in the second brake circuit, and the brake actuator is connected via the first control line to the first valve in order to control the first valve, and via the second control line to the second valve in order to control the second valve. By actuating the brake actuator, for example by means of a brake pedal, which is operatively connected to the brake actuator, it is possible to regulate the brake pressure in the respective brake circuits by controlling the first and second valves, and, therefore, to regulate the braking force which acts on wheel brakes, which are connected to the respective brake circuits and can be controlled by means of a pressure medium.
A disadvantage of such conventional brake systems is that malfunctions or failures, in particular, in the sections comprising brake actuator—control lines—valves, are not detected.